The Influence Of Exercise On Meal Size And Body Weight Of Obese Rats And Its Mechanism

Aims:Research the effects of food intake related endocrinological hormones on serum and hypothalamic of obese rats by acute and long time of exercise and discuss the neuroendocrinology mechanisms of weight loss by exercise.Methods:Diet induced obese rats go throuth two experimental models: acute exercise experiment and 8 weeks exercise experiment.The rats run at a speed of 20 m min-1,50 slope on the treadmeal for 40 min one times on the acute experimental model and every five days for 8 weeks on the chronic experimental model.On the day they were sacrificed,rats from the acute experimental exercise group were randomly divided into six subgroups,namely C,EO,E1,E3,E12 and E24,which respectively were named as the preexercise control group,0 min postexercise group,one hour postexercise group,three hour postexercise group,twele hour postexercise group and twenty hour postexercisegroup.On the chronic exercise experiment model,the rats are divided long exercise group and long control group and the rats had rest for 24 hours before they are sacrificed after the last day.We determined the concentrations of ghrelin,obestatin and NPY on serum and hypothalamic of obese rats at once,one hour,three hour,12 hour and 24 hour after acute exercise and the concentrations after eight weeks' exercise by using RIA;we also determined the receptor GHSR-1a mRNA of ghrelin,GPR-39 mRNA of obestatin and NPY mRNA on the hypothalamic tissues by RT-PCR.Results:1) Compared with normal weight rats,the obese rats had distinct differences on body weight,BMI and serum preferences.The concentration of ghrelin and the ratio of Ghrelin/Obestatin had a decline tendency on serum,obestatin had an up tendency and NPY was higher than the normal weight rats distinctly.But on the hypothalamic tissues,the concentrations of ghrelin and obestatin decreased greatly,the ratio of Ghrelin/Obestatin increased,NPY had a decline tendency lightly.The ghrelin receptor GHSR-1a mRNA decreased distinctly,NPY mRNA had no change and we couldn't find GPR-39 mRNA on hypothalamic.2) After acute exercise,appetite and food size decreased greatly on obese rats and recovered at the point of 12 hours;Glu and other preferences on plasma decreased and recovered at the point of 3 hours;on every time points,the serum concentrations of ghrelin and obestatin had no changes, but NPY decreased distinctly.3) After acute exercise,the concentrations of ghrelin and obestatin on hypothalamic decreased before the point of 12 hours,then they increased greatly and recovered to preexercise after 24 hours;NPY increased at once after exercise and recovered after 24 hours;The receptor GHSR-1a mRNA of ghrelin and NPY mRNA had no changes after exercise and we couldn't find GPR-39 mRNA on hypothalamic too.4) After 8 weeks oxygen exercise,the obese rats expended a great deal energy with no food intake increased,on the contrast,their food size decreased greatly;Exercise alone had no effects on serum ghrelin and obestatin,but on hypothalamic,ghrelin and obestatin decreased distinctly,NPY increased greatly;The receptor GHSR-1a mRNA of ghrelin had no change,but NPY mRNA increased distinctly after exercise.Conclusions:1) Ghrelin mediated food intake and energy metabolism post exercise through hypothalamic centers.2) Obestatin- GPR-39 may be had no use on energy homeostasis.3) The ratio of Ghrelin/Obestatin must be very important on the etiology of obese rats.